Update to SQLAlchemy 2.0+

[RudolfCardinal]

Because (1) generally a good idea, and (2) specific desirability for the Databricks connector, https://github.com/databricks/databricks-sql-python

[martinburchell]

There is a clear upgrade path documented https://docs.sqlalchemy.org/en/20/changelog/migration_20.html including turning on "Removed in 2.0" warnings in 1.4

[RudolfCardinal]

Relevant links from elsewhere:

• cardinal_pythonlib: SQLAlchemy 2 update, and bump to 2.0.0 RudolfCardinal/pythonlib#23
• Databricks and SQL types: Is there a generic method for converting SQL column types, as text, to SQLAlchemy column types? sqlalchemy/sqlalchemy#12230